Grundfos MAGNA3 D Installation And Operating Instructions Manual page 39

8.11.5 Heat energy monitor
The heat energy monitor calculates the heat energy consumption
within the system. The built-in flow estimation needed for the
calculation has an inaccuracy of ± 10 % of the maximum flow.
Also, the temperature measurements needed for the calculation
have some inaccuracy depending on the sensor type. Therefore,
you cannot use the heat energy value for billing purposes.
However, the value is perfect for optimization purposes in order to
prevent excessive energy costs caused by system imbalances.
The flow and volume accuracy is calculated and shown in the
display, see sections "Estimated flow", page 44, and "Accuracy of
values", page 44.
The heat energy monitor requires an additional
temperature sensor installed in the flow pipe or
return pipe depending on where the pump is
installed.
kWh
t
F
t
R
Fig. 53 MAGNA3 with built-in heat energy monitor
You can measure both heating and cooling in the same system. If
a system is used for both heating and cooling, two counters are
automatically shown in the display. See section "Heat energy",
page 44.
Monitoring heat energy in multipump systems
In a multipump system, the master pump calculates the heat
energy regardless of which pump, master or slave, is running.
If the master loses power or has a fault on the external sensor,
the accumulation of heat energy will not be counted until the
master is powered back on or the external sensor error is
remedied. If the master is replaced, the heat energy values for
the system is reset.
8.11.6 External setpoint function
You can use the analog input to influence the setpoint externally.
Here, a 0-10 V or 4-20 mA signal controls the pump speed range
in a linear function. The range of control depends on the minimum
speed, power and pressure limits of the pump. See figs 54 and
55.
(user setpoint)
H
Resulting
setpoint
Analog input
0 2
Fig. 54 External setpoint function, 0-10 V
Control
0-2 V (0-20 %) Resulting setpoint is equal to minimum.
Resulting setpoint is between minimum
2-10 V (20-100 %)
and user setpoint.
Fig. 55 Control range and setpoint
The external setpoint function operates differently depending on
the model. For models A, B and C, the maximum speed is often
obtained at voltages lower than 10 V, as the span of control is
limited.
In models newer than A, B and C, the internal scaling has been
optimized making the dynamic area bigger, thus giving a better
control of the pump speed when using the external setpoint
function.
The same applies if the pump is receiving a setpoint from Building
Management Systems.
V
10
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